Whatsapp founders leap onto this year's global rich list following Facebook's $19 billion acquisition

*.Whatsapp founders Jan Koum and Brian Acton were a last-minute addition to this year's list of global billionaires
*.The firm was acquired by Facebook in February for a total of $19 billion
*.Koum is set to get $6.8 billion, while Acton is said to be worth $3 billion
*.Other new entries on the list include Sheryl Sandberg and Michael Kors
*.Bill Gates earned $9 billion last year putting him back at the top of the list
*.Mark Zuckerberg came in at number 21 on the list and his net worth jumped from $15.2billion to $28.5billion over the past year
*.Biggest year ever for women as Forbes found 172 female billionaires (up from 138 last year) to include on the list of 1,645 people
The co-founders of popular instant messaging service Whatsapp have become a last-minute addition to this year's list of global billionaires.
Jan Koum and Brian Acton made Forbes' annual rich list in February after Facebook offered a total of $19 billion to buy their company.
The deal gives Koum a fortune of $6.8 billion, while partner Acton is said to be worth at least $3 billion according to Forbes.